1. Field of the Invention
The present invention relates to an air bag device, and particularly to an air bag device provided in vehicles such as automobiles and expanding to unfold in an interior of the vehicle so as to protect a vehicle occupant.
2. Description of the Related Art
Heretofore, an example of an air bag device provided in vehicles such as automobiles and expanding to unfold in an interior of the vehicle so as to protect a vehicle occupant has been disclosed in Japanese Utility Model Application Laid-Open (JP-U) No. 3-52265.
In an air bag device as shown in FIG. 6, an air bag body 70 is formed so as to have a double structure comprised of an inner air bag body 72 and an outer air bag body 74. A large vent hole 76 is formed in the outer air bag body 74 and a small vent hole 78 is formed in the inner air bag body 72. The vent hole 76 formed in the outer air bag body 74 is provided with a lid 80. The lid 80 closes the vent hole 76 until expansion (unfolding) of the outer air bag body 74 is substantially completed, and the lid 80 opens the vent hole 76 after the expansion of the outer air bag body 74 has been substantially completed. As a result, in a case in which a vehicle occupant abuts against the air bag body 70 after the expansion of the outer air bag body 74 has been substantially completed, reaction force is applied from the air bag body 70 to the vehicle occupant, and the vehicle occupant is protected.
In the above-described air bag device, as shown in FIG. 6, the small vent hole 78 is formed in the inner air bag body 72 and the large vent hole 76 is formed in the outer air bag body 74. Therefore, the quantity of gas which is allowed to pass through the vent holes 76 and 78 cannot be controlled in accordance with a physical constitution of a vehicle occupant abutting against the air bag body 70. As a result, in the air bag device shown in FIG. 6, reaction force applied from the air bag body 70 to the vehicle occupant when the vehicle occupant abuts against the air bag body 70 is made most suitable only for a vehicle occupant of a standard (average) physical constitution.
In view of the above-described facts, an object of the present invention is to provide an air bag device in which proper reaction force corresponding to a physical constitution of a vehicle occupant abutting against an air bag body can be generated.
In accordance with a first aspect of the present invention, there is provided an air bag device having an air bag body which expands to unfold in an interior of a vehicle, the air bag body comprising: an outer air bag body having vent holes communicating with an exterior of the air bag body; and an inner air bag body having a capacity smaller than that of the outer air bag body and unfolding in an interior of the outer air bag body, wherein the inner air bag body is formed so as to have a high gas permeability, and when a vehicle occupant abuts against the outer air bag body, a portion of the outer air bag body pressed by the vehicle occupant abuts the inner air bag body so as to control a quantity of gas flowing from the inner air bag body into the outer air bag body.
Accordingly, in a case in which the vehicle occupant abuts against the outer air bag body after the air bag body has unfolded, a portion of the outer air bag body pressed by the vehicle occupant abuts the inner air bag body and the quantity of gas flowing from the inner air bag body into the space formed between the inner air bag body and the outer air bag body is controlled. As a result, the quantity of gas flowing from the inner air bag body to the outer air bag body changes in accordance with a physical constitution of the vehicle occupant abutting against the air bag body, and the quantity of gas escaping from the vent holes of the outer air bag body to an exterior of the air bag body also changes due to the same reason. Namely, in a case in which a small-built vehicle occupant abuts against the outer air bag body, an area of a portion at which the outer air bag body and the inner air bag body abut each other is small and a region of the inner air bag body through which gas is allowed to pass becomes wide. Therefore, the quantity of gas flowing from the inner air bag body into the space between the inner air bag body and the outer air bag body increases and the quantity of gas escaping from the vent holes of the outer air bag body to an exterior of the air bag body also increases. As a result, it is possible to prevent reaction force, which is applied from the air bag body to the vehicle occupant when the vehicle occupant abuts against the air bag body, from unnecessarily becoming large (from becoming larger than desired one). On the other hand, in a case in which a largely-built vehicle occupant abuts against the outer air bag body, an area of a portion at which the outer air bag body and the inner air bag body abut each other is large and a region of the inner air bag body through which gas is allowed to pass becomes smaller. Therefore, the quantity of gas flowing from the inner air bag body into the space between the inner air bag body and the outer air bag body decreases and the quantity of gas escaping from the vent holes of the outer air bag body to an exterior of the air bag body also decreases. As a result, it is possible to prevent reaction force, which is applied from the air bag body to the vehicle occupant when the vehicle occupant abuts against the air bag body, from unnecessarily becoming smaller (from becoming smaller than desired one). In other words, suitable reaction force can be generated correspondingly to the physical constitution of the vehicle occupant abutting against the air bag body.
Further, according to a second aspect of the present invention, in the air bag device provided by the first aspect, the inner air bag body is made of a cloth material having a large number of vent holes formed therein.
Accordingly, in addition to the structure provided by the first aspect of the present invention, it suffices that a large number of vent holes be formed an inner air bag body. As a result, suitable reaction force can be generated by a simple structure so as to correspond to the physical constitution of the vehicle occupant abutting against the air bag body.
In accordance with a third aspect of the present invention, in the air bag device provided by the first aspect, the inner air bag body is made of a cloth material having a high gas permeability.
Accordingly, in addition to the structure provided by the first aspect of the present invention, it suffices that an inner air bag body be made of a cloth material having a high gas permeability. As a result, suitable reaction force can be generated by a simple structure so as to correspond to the physical constitution of the vehicle occupant abutting against the air bag body.
Still further, in accordance with a fourth aspect of the present invention, there is provided an air bag device having an air bag body which unfolds in an interior of a vehicle, the air bag body comprising: an outer air bag body; and an inner air bag body having a capacity smaller than that of the outer air bag body and unfolding in an interior of the outer air bag body, wherein the outer air bag body includes at least one first hole formed therein, and the inner air bag body includes communication means which is formed at least on a facing surface thereof substantially facing a vehicle occupant at the time of unfolding the air bag body, the communication means being provided to allow communication between an interior of the inner air bag body and a space formed between the inner air bag body and the outer air bag body.